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. 2014 Mar 31;2014:750459. doi: 10.1155/2014/750459

Figure 1.

Figure 1

Epigenetic mechanisms. DNA is wrapped around proteins called histones; this forms the core DNA package called the nucleosome. When the DNA is tightly wrapped, transcription factors cannot bind and transcription is repressed. When the DNA is more loosely wrapped, transcription is more active as transcription factors can bind. DNA methylation is when a methyl group is added to the DNA strand and is associated with transcriptional repression [58]. Histone acetylation is the addition of acetyl groups to the histone tails and this is associated with transcriptional activation. Histone deacetylation is the removal of acetyl groups which is associated with transcriptional repression [59].